Flat screen frame



June ll, 1935.

J. J. MORAVEC FLAT SCREEN FRAME Filed June 27, 1934 4 Sheets-Sheet lJune 1l, 1935. J, MORAVEC 2,004,507

FLAT SCREEN FRAME Filed June 27, 1934 4 Sheets-Sheet 2 .Inu @n fb f':away/7 .IMO/'avec June 1l, 1935. 1 J, MORAVEC l 2,004,507

FLAT SCREEN FRAME Filed June 27, 1934 4 SheetsSheet 3 June 11, 1935. J.J. MoRAvEc FLAT SCREEN FRAME Filed June 27; 1934 4 Sheets-Sheet 4Patented-June 11, 1935 UNITED STATES PATENT OFFICE,

23 Claims.

My invention relates to devices commonly known as vibratory at screensused for the refining of wood pulp in paper making, and, in particular,for the separating of ne wood fibers suitable for further steps in theprocesses of paper manufacture, from wood slivers, bark, dirt and otherextraneous matter. As is well known, this separation or screening of thefine fibers is accomplished by drawing the pulp thru flat metalscreen-plates provided with fine slots, generally about 1/100 of an inchwide an'd about 4 inches long, and, as the pulp passes over thesescreen-plates, the fine bers are drawn thru the slots, 'while thecoarser fibers and undesirable particles pass over the top of the screenplates and are later either worked over or wasted. To aid in drawing thener fibers thru the slots, a suction is established by placing aflexible sheet, called a diaphragm and usually made of heavy rubberunder the screen-plate supports, and causing this diaphragm to bevibrated by arms bearing on a revolving cam, or by other means.

The screen plates are supported in a shallow rectangular vat or trough,usually about 31/2 feet wide, having a gentle slope longitudinally fromthe inflow to the outflow end. It is customary to make the screen-platesupports, the cross pieces, sides of the vat, braces and othersupporting frame members of wood. Heretofore the heavy metal screenplates were supported onA longitudinal bars or beams and transversebars, generally made of hard wood, and the screen plates were secured tothese transverse bars by screws and other means arranged to hold thescreen plates firmly in place, but to permit them to be taken up orremoved when necessary. However, the continuous vibration of the rubberdiaphragms causes a sympathetic vibra'- tion to be imparted to thescreen plates, transverse bars, and other supporting frame members, withthe result that the screws gradually work loose, the surfaces of thescreen supporting members fray and chip off, wood splinters frequentlydrop into the refined pulp below the screens, and repairs are necessaryat frequent intervals. Furthermore, the continual water logging actionto which the transverse wooden' bars are subjected, together with thedeteriorating action of the chemicals in the pulp, causes these bars togo to pieces much more rapidly than would ordinarily be the case. Thesewooden bars also become coated with slime, and, unless they are scraped01T regularly, this slime mixes with the refined pulp below the screenplates.

The object of my invention is to overcome these objectionable features,and to provide a. nat-screen frame and supports of suitable con- 5struction and material to resist the deteriorating effects of constantvibration and chemical action.

I attain my object by providing a screen frame built in sections, eachsection comprising a uni- 10 tary structure, or, if built up of separateparts, the parts so arranged that they will, when assembled, constituteunitary sections, so that individual frame sections can readily beremoved, thereby facilitating inspection and repairs of separatesections when required without necessitating the taking apart of thevibratory atscreen as a whole.

A further desirable result attained by my invention is that all surfaceswhich come in contact with the refined pulp are of metal and thus thesloughing off into the refined pulp of the undesirable coatings andportions of Wood surfaces is avoided.

Another feature of my invention is that the means provided for lockingthe screen frame members in place is so housed as to exclude all pulpmaterial therefrom, which pulp material would otherwise interfere with,and cause deterioration of the operative parts of said means.

The above mentioned as well as other features of my invention arehereinafter fully described with reference to the accompanying drawings,in which Fig. 1 is a sectional view of the vat containing 35 myscreen-plate supports taken longitudinally along the center line of thevat; the screen frame as here shown consisting of longitudinal andtransverse members cast into one piece for each section or suctionchamber;

Fig. 2 is a transverse section across the sam vat but drawn to a largerscale;

Fig. 3, sheet 2, is a drawing, in a diagrammatic isometric perspective,of my vat, screen plates and screen frames, with some of the screenplates removed and portions of the supporting frame members broken awayto show details of their construction, the screen frames being of the same construction as shown in Figs. 1 and 2;

Fig. 4, sheet 1, shows a block-bar holding the frame;

Fig. 5, sheet 1, is bar taken on line used in screen plates down on thescreen a cross-section of the lock- 5 5 of Fig. 4; 55

portion of my one-piece frame, illustrating specifically an optionalmeans of fastening adjacent frames together;

Fig. '7, sheet 4, shows a longitudinal sectional view of the vat,similar to Fig. l, but with screen plate supports made up of individual,removable transverse bars and spacing plates;

Fig. 8, sheet 1, shows the spacing plate employed with the individualremovable bars in the construction illustrated in Fig. 7 for woodenvats;

Fig. 9, sheet 4, is a larger sc'ale, vertical section of a portion ofthe side of the wooden vat, showing, partly in section, used for holdingdown lock-bars and screen plates on the screen frame;

Fig. 10, sheet 4, is a view of the rear face of my lock-screw-clamp,that is, the face adjacent to the side of the vat;

Fig. 1l, sheet 4, is a horizontal section on the line lI--II of Fig. 10,looking down;

Fig. 12, sheet 4, is a side view of my lockscrew-clamp;

Fig. 13, sheet 4, is a horizontal section on the line i3-I3 of Fig. 12looking up, with the nut and screw inside the lock-screw-clamp removed;

Fig. 14, sheet 4, is a plan view of the nut in the interior 'of mylock-screw-clamp;

Fig. 15, sheet 3, is a fragmentary view, in perspective, of a side ofone of the transverse bars used in the construction illustrated in Fig.7 for wooden vats;

Fig. 15a, sheet 3, is a fragmentary view, in perspective, of a side ofone of the middle bars used in the same construction;

Fig. 16, sheet 3, is a vertical section of the side of a metal vatcorresponding to the section of the wooden vat shown in Fig. 9;

Fig. 17, sheet 3, is a longitudinal section of a metal vat with part ofthe screen plates broken away and the middle bar, lock-bar andlockscrew-clamp removed;

Fig. 18, sheet 3, is a the middle bar of the a metal vat;

Fig. 18a, sheet 3, is a similar view, on reduced scale, of one of theother transverse bars adapted for use i'n a metalvat;

Fig. 19, sheet 2, is a fragmentary longitudinal section of a vatcontaining a modied construction of part of my screen frame; and

Fig. 19a, sheet 2, is a cross section of two adjacent side bars of myscreen frame illustrating another modified construction.

Referring rst to Figs. 1, 2 and 3: a, a' and a2 are longitudinal beams,and b, b are transverse beams in the supporting frame of the vat. c andc' are the sides of the vat. The bottom of the vat is closed by seriesof rubber diaphragms d.

In my screen frame as illustrated vby Figs. 1, 2 and 3, which Idesignate as my one-piece construction, each frame is rectangular inshapeabout 2 feet wide and 31/2 feet long-is made to hold two screenplates n, and is composed of three integral, transverse bars e, f and e'spaced apart by integral end members g, and intermediate braces h, h andi, fi', which elements together constitute one frame unit. The sides e',e and the end portions g of the frame are made with flanges as e2 at thebottom, so as to provide broad bearing faces resting firmly on top ofthe rubber diaphragm d, which in turn is supported on the transversebeams b, and

view on reduced scale of frame adapted for use in my lock-screw-clamp.

Fig. 6, sheet 3, shows, in perspective, a cornerthe longitudinal beamsa, a'. The bottom edges of the middle bar f, and the intermediate bracesh, h', and 7', a" are spaced from the bottom of the frame so as toprovide ample clearance space above the diaphragm d within the cham-4ber formed by each screen frame. The sides e and e and ends g of theframe are made with a ange 7cv at the top on which the screen plates nrest. The middle bar f of the frame is made with opposite lateral angesm and m', level with the top ange Ic of the ends g, and surmounted byoverhanging beveled shoulders o and o'. The sides e and e' are made withvertical iianges k2 (see Fig. 1 and Fig. 6) adapted to be engaged by theheads of bolts k3 extending thru the side of the vat, as shown in Fig.2. This construction eliminates the use o! the iron tie-rods heretoforeemployed and extending across the vat to prevent any spreading of thesides. These former tie-rods, which were ordinarily made of wroughtiron, and passed thru the suction chambers between screen plates anddiaphragms, became coated with rust as a result of their contact withthe wet pulp, and the scaling off of this rust into the refined pulp wasa troublesome feature of the customary type of wooden frames. Thisobjectionable feature I have avoided by substituting the bolts k3 andkeeping these bolts out of contact with the wet pulp.

The screens are rectangular metal plates, portions of which are shown byn in Fig. 3, provided with narrow parallel transverse slots n', theslots thus extending longitudinally along the top of the vat. Theseslots are generally about 4 inches long and 1/100 of an inch wide, aspreviously mentioned. The side edges o! the screen plates n are beveled;one beveled edge of each screen plate is engaged by the beveled edge ofone of the shoulders o or o of the middle bar f, and the other bevelededge of each screen plate is engaged by the head p' of a lock-bar p (seeFigs. 4 and 5). The lockbar p, which has a T-shaped cross-section, asshown in Fig. 5, has the edges ofits head p beveled to correspond to thebeveled edges of the screen plates.

'I'he exterior faces o1` the sides e and e' of the frame are providedwith lugs q to keep adjacent frames spaced suiiciently from each otherso as to permit lock-bars to be inserted between them. Holes may bedrilled thru these lugs and thru the sides of the frames, and screwbolts q' inserted in these holes for the purpose of bolting adjacentframes together in the vat,

or adjacent frames may be fastened together by external locking lugs, aswill be explained later on. After the screen plates n have been placedin position on the top of the frames the lock-bars are dropped intoplace, and the screen plates cannot be removed or lifted out of placewithout lifting up the lock-bars.

The lock-bars p are heldl in place by means of a lock-screw clamp rplaced at each end of the lock-bars p. The details of my lock-screwclampare shown in Figs. 9 to 14, sheet 4. The lock-screw-clamp comprises ascrew s on which is threaded a clamping nut t, having a lip l. The screws is rotatably supported in the housing u and the top of the screw,which extends thru the top of the housing v, has a head w of hexagonalcross-section, or similar convenient shape, to facilitate the turning ofthe screw. A bearing ring a: is placed between the bottom of the screwhead w and the top of the housing v. A pin y is inserted in the neck oithe housing v and is engaged by a circumferential groove s' in the shankof the screw. The pin y is held in place by a ferrule or sleeve zdropped over the neck of the housing v. The clamping nut t, which israised or lowered by the turningof the screw s, is shaped as shown bythe plan view in Fig. 14, and the side views in Figs. 9 and 11. It issquare, with two sides cut away as at 2 and 3, Fig. 14, and provided onone side with a projecting lip 4 the top surface of which extendsobliquely upward. The lock-screw-clamp housing u encloses the clampingnut t on three sides I4, I9, I5. 'I'he interior of the housing vcorresponds to the square shape of the clamping nut t and permits theclamping nut to move up and down on the screw s'but prevents anyrotation of the clamping nut. 'Ihe interior of the housing is made withtwo rectangular guide ribs 5 and 6 (Fig. 11) on which the clamping nut tslides. Figs. 11 and 13 show horizontal cross-sections of the housingfrom which it will be seen that one face thereof is open to permit freevertical movement of the projecting lip 4 of the clamping nut. Atregular intervals, corresponding A to the location of the lock-bars p,indentations are cut into the sides of the vat to accommodate recessedplates 'I (see Fig. 9), which are fastened to the vat sides by bolts 1a.These plates are 'provided with a recess 1b, to accommodate theprojecting side'portions I4, I5 of the housing v, and with a downwardprojecting locking flange 9 adapted to engage the projecting lip 4 ofthe clamping nut t.

vThe bottom of the housing v of the lockscrew-clamp is made with a lug I0 tapered at its ends and projecting downwardly a distance slightly lessthan the thickness of the screen plate n and adapted to slide betweenthe beveled edges of the screen plates. The lock-bar p is made slightlyshorter than the frame or the screen plates so that the end of thelock-bar will extend under the bottom of the housing v of thelock-screw-clamp up to the lug I0. 'I'he end of the lock-bar p thusprevents any movement of the lug I0 and consequently any movement of thebottom of the housing v out away from the adjacent vat side. A gasket IIof rubber or other packing material is inserted in the cavity I2 at thebottom of the housing v for the purpose of making the connection betweenlockscrew-clamp and lack-bar p absolutely tight.

The front side I3 of the lock-screw-clamp housing (see Figs. 10, 11 and13) extends out beyond the 'side faces I4 and I 5, as at I3a, and thetops of the side faces have pendent flanges I6 and I'I (Fig. 10). 'I'heends of the screen plates n are held down by wooden bars I8, see Figs. 1and 3. These bars are made with a longitudinal groove on the bottom inwhich is inserted a gasket II a, similar to and in line with the'gasketII in the bottom of the hous'n" If the lock-screw-clamp r, and anotherlongitudinal groove and gasket IIb on the side adjacent to the side ofthe vat. The purpose of these is to make the connections between thebars I8 and the screen plates and between the bars and the vat sidesabsolutely tight when the lockscrew-clamps are tightened. The ends ofthe bars I8 are cut out at the top and front faces, as shown at I8a inFig. 1, to fit into the sides of the lock-screw-clamp housing, so thatthe front face of the wooden bars I8 will be flush with the front faceof the lock-screw-clamps r,

iand the pendent flanges I6 and I'I will flt over the ends of the barsI8.

By the turning of theA screw s of the lockscrew-clamp, the clamping nutt is raised and its lip 4 is interlocked with the flange 9 of the platef 'I, the end of the lock-bar is held down firmly, and the sides of thescreen plates engaged by the lock-bar are held down on top of thescreenframe. Simultaneously the flanges I6 and I I of the housing v bear downon the ends of the engaged bars I8, causing the latter to bear down ontop of the ends of the screen plates. The

.sloping adjacent faces of the lip 4 of the clamping nut t and flange 9of the plate 'I pull the lock-screw-clamp r firmly against the vat sideand hold it there. Thus, no pulp can get inside the housing of thelock-scre'w-clamp, which formerly was one ofy the chief difficulties inthe use of the screw -clamp heretofore employed.'

The front faces ofthe lock-screw-clamps, engaging the adjacent ends ofthe bars I8, hold the bars I8 tight against the sides of the vat. As aresult of this sealing of joints there is no suction loss in the suctionchambers below the screens and it is impossible for any pulp to get intothe suction chambers except thru the narrow slots in the screen plates.

The lock-bar p is slightly concave longitudinally, as shown onexaggerated scale in Fig. 4. However, when the ends are pressed down bythe lockscrew-clamps the top becomes straight. Having the top madeslightly concave insures the firm pressing-down of the screen plates bythe lock-bar along their entire side edges.

Each frame, as described, constitutes an individual suction chamber witha rubber diaphragm for the base and a pair of screen plates for the top.A rod or plunger :c attached to the center of the diaphragm d, andreciprocated by a cam, or other means, not shown, causes the diaphragmto vibrate up and down and, as well known, the suction resulting fromsuch movement of the diaphragm draws the fine pulp fibers through theslots of the screens.

Instead of fastening adjacent frames together by bolts such as q' theoutside faces of the frame sides e, e' may be made with interlockinglugs 42 as shown in Fig. 6, by which means adjacent frames are-heldfirmly together when two frames are dropped into position side by sidein the vat. Of course, when the frame sides are made with theseinterlocking lugs the bolts q' are dispensed with and the holes whichwould be drilled for them are omitted.

The advantages of my frame, as now will be apparent, are: First of all,there is no wood to splinter and wear away, no screws to be replaced, orother parts to work loose with the constant vibration. Secondly, theremoval of the screen plates is a very simple matter, especially ascompared with the amount of work required in removing the screen platesof the ordinary flat vibratory pulp screens. Further, the removal of theentire frame is quite simple, and particularly the removal andreplacement of the rubber diaphragm can be done easily, and requiresremoval of one frame only. My one-piece frame is suitable for use in theordinary and when so installed constitutes a metal lining for the vatsince the wooden sides of the vat are protected from contact with thepulp. But, while my screen frame is especially adapted for use with thepresent type of Wooden vats, of course it is not limited in use to anyparticular type of vat.

The foregoing description covers my metal flat screen frame made as aone-piece or unitary. structure. It may, however, bebuilt of separablemembers, and this construction has advantages in the transportation offrame members from the place of manufacture to the place of use.

When so 'designed my screen frame sections entail certain differences inconstruction readily seen by comparison with my one-piece sections shownby Fig. 3.- My built-up frame sections consist of end members 26 (Fig.8), the equivalent.of end members g of Fig. 3, side members 26 (Fig.15), the equivalent of members e and e' of Fig. 3, and middle barsequivalent of members f of Fig. 3.' In this construction whereby screenframe is\built up of separable parts, I do not considerthe braces suchas h, h. of Fig. 3 necessary.

The end members 2D (Fig. 8) have rectangular cut-out portions or notches2| at the bottom and other cut-out portions or notches 22 at the top.The end members 20 are designed to serve as liner plates for the innersides of the vat. The side members 26 (Fig. 15) are formed at their endswith projecting lugs 44 at the top, and the middle bars 23 (Fig. 15a)are formed at their ends with projecting lugs 43 at the bottom. The lugs43 fit into the bottom notches 2| of the end members 20. The uppernotches 22 of the end members 20 are made exactly large enough toaccommodate the lugs 44 of a pair of bars or side members 26.

This built-up frame assembly is shown by Fig. 7, representing a-longitudinal section of a wooden vat in which screen frame assembly isinstalled. The side members 26, like their equivalents e and e', haveexternal lugs 21, for keeping the sides of adjacent sections spaced fromeach other suiliciently to allow lock-bars 28 to be dropped betweenthem, and they have end flanges 46 adapted to engage the heads of boltsIc1 extending thru the sides of the vat. Adjacent side members 26 may beheld together either by bolts 29 or by interlocking lugs similar to thelug 42 of Fig. 6. The middle bars 23 are provided with screen plateengaging elements 24, similar to the elements m, m and o, o' of theintegral middle bar f of Fig. 3. The screen plates 25 are also held downby the lockbars 28 andby the bars I6' extending over the ends of thescreen plates. The bars I6 and lock-bars 28 are held down bylock-screw-clamps r already described. The end members 20, which act asspacer plates for the side members 26 and middle bars 23 as well asliner plates for the vat sides, may be made in convenient lengths, forexample, as shown in Fig. 8, in lengths corresponding to the width ofeach screen frame section.

My screen frame, when constructed 0f separate members; possesses thesame advantages over the old fashioned Wooden screen frames as alreadypointed out with reference to my onepiece screen frame. It is furthersuitable equally as well for a metal vat as for a wooden vat.

Fig. 16, sheet 3, shows a vertical section of a side of a metal vat; andFig. 17 shows a longitudinal section of the metal vat with portions ofthe screen frame removed and part of the screen plates broken away. Thesides 30, which may be made in sections of convenient length joinedtogether in any suitable manner so long as the joints areabsolutelytight and the inside of the sections are flush with each other, are

23 (Fig. 15a), thev preferably made with vertical ribs or webs 3| on theback, with top and bottom flanges 32 and 32' (see Fig. 16), and alongitudinal ridge 33 on the bottom surface adapted to engage a shoulderon the beam 34 of the supporting frame for the vat. Figs. 18 and 18ashow a middle bar and a side member, respectively, of my built-up screenframe as adapted for the metal vat. The lower portion of the vat sidesis of greater thickness than the upper portion, making a ridge 38between upper and lower portions. In the lower portion of the vat sides,at points constituting the location of the middle bars of the framesections, grooves are made by pairs-of blocks 39 just wide enough toaccommodate the ends of the middle bars 40. At the ends of the middlebars 40 (see Fig. 18) the bottom iianges 4| are cut away so as not tointerfere with the blocks 39. Thus, when the middle bars are droppedinto place, they are securely held in the vat sides. The side members(Fig. 18a) are made with vertical flanges 41 and with external spacinglugs 48, and adjacent side members are held together either by bolts orby interlocking lugs (such as 42 in Fig. 6) in the manner alreadydescribed. The vat sides are made with rectangular depressions or wells35 containing downward projecting flanges 36 at the top, said flangesbeing adapted to engage the projecting lip 4 of the lock-screw-clamppreviously described. The vat sides are also provided with holes locatedbelow the wells 35 thru which bolts 31 are inserted, and the heads ofthese bolts are engaged by the flanges 41 at the ends of the sidemembers 45. The method of locking the screen plates in place is exactlythe same as that described before.

In the specification thus far the screen plates have been described as'having beveled side edges, with the middle bars provided with lockingheads to engage adjacent edges of the screen plates; and lock-bars areprovided to engage the other sides of the screen plates. Thisconstruction, however, may be modified if desired; 'the screen platesmay be made with straight, instead of beveled edges on one side, and thelocking head of the middle bar may be dispensed with. Also the lock-barsmay be modified or dispensed with entirely.

One such modification is illustrated in Fig. 19 (sheet 2)', showing afragmentary longitudinal section of a vat, in which 5| represents thediaphragm, 52 is the middle bar having opposite lateral flanges 53 atthe top. The related ends of the screen plates have straight edges 56,and the screen plates ends are fastened to said flanges 53 of the middlebar by screws 51.

58 is a modified form of lock-bar. As apparent, this lock-bar has nopendent shank. The lock-bar 58 is secured in place by tie rods 59extending down thru the transverse frame member of the vat support, suchbolts being spaced, for example, about l0 inches apart.

A still further modification of the means for securing the screens inplace is shown by Fig. 19 (sheet 2). Here the lock-bar has been entirelydispensed with, the edges of the screen plates over the side bars 54 aremade straight instead of beveled, and adapted to touch each other, andare fastened on the top flanges of the bars 54 by screws 49. In suchcases the top flanges of the bars 54 are made broad enough to touch eachother.

In all other respects my screen frame construction would be the same asabove described,

including longitudinal bars extending along the vat sides over the endsof the screen plates and the lock-screw-clampsfor holding thelongitudinal bars, screen plates and screen supporting frame sectionsrmly in place.

I claim:

1. A flat screen assembly comprising adjacent rectangular all metalsections, each composed of sides, ends, a transverse middle bar, andscreen plates, said middle bar being spaced from the bottom of theframe, the middle bar provided with a locking head for engaging adjacentscreen plates, means-for connecting the opposed sides of adjacent framesections so spaced as to receive a screen plate lock-bar between them, ascreen plate lock-bar adapted to be inserted between said opposed framesides, said lock-bar provided with a head adapted to engage the sides ofadjacent screen plates, and means for securing said lock-bars in place.

2. A flat screen assembly comprising adjacent rectangular all metal,one-piece sections, each composed of sides, ends, a transverse middlebar, braces and screen plates, said middle bar and braces being spacedfrom the bottom of the frame, the middle bar provided with a lockinghead for engaging adjacent screen plates, means for connecting theopposed sides of adjacent frame sections so spaced as to receive ascreen plate lock-bar between them, a screen plate lockbar adapted to beinserted between said opposed frame sides, said lock-bar provided with ahead adapted to engage the sides of adjacent screen plates, and meansfor securing said lockbars in place.

3. In combination with a vat a at screen assembly comprising adjacentrectangular all metal sections, each composed of sides, ends, atransverse middle bar, and screen plates, said middle bar being spacedfrom,the bottom of the frame, the middle bar provided with a lockinghead for engaging adjacent screen plates, means for connecting theopposed sides of adjacent frame sections so spaced as to receive ascreen plate lock-bar between them, a screen plate lock-bar adapted tobe inserted between said opposed frame sides, said lock-bar providedwith a head adapted to engage the sides of adjacent screen plates, meansfor securing said lock-bars in place, the side walls of the vat providedwith recessed plates having a lockange, and said lock-bar securing meansincluding a screw operated locking lip engaging with said lock-flange.

4. In combination with a vat a flat screen assembly comprising adjacentrectangular all metal sections, each composed of sides, ends, atransverse middle bar, and screen plates, said middle bar being spacedfrom the bottom of the frame, the middle bar provided with a locking.head for engaging adjacent screen plates, means for connecting theopposed sides of adjacent frame sections so spaced as to receive ascreen plate lock-bar between them, a screen plate lock-bar adapted tobe inserted between said opposed frame sides, said lock-bar providedwith a head adapted to engage the sides of adjacent screen plates,`meansfor securing said lock-bars in place, the side walls of the vat providedwith recessed plates having a lock-flange, and said lock-bar securingmeans including a screw operated locking lip engaging with said lockflange, a series of overlying bars extending over the ends of saidscreen plates, said lock-bar securing means including a housing formingwith said overlying bars continuous wall surfaces constituting the innersides of a trough over the screen plates.

5. In combination with a vat a fiat screen assembly comprising adjacentrectangular sections, each composed of sides, ends, a transverse middlebar, and screen plates, said middle bar being spaced from the bottom ofthe frame, the middle bar provided with a locking head for engagingadjacent screen plates, means for connecting the opposed sides ofadjacent frame sections so spaced as to receive a screen .plate lock-barbetween them, a screen plate lock-bar adapted to be inserted betweensaid opposed rame sides, said lock-bar provided with a head adapted toengage the sides of adjacent screen plates, -means for securing saidlock-bars in place, such means comprising a vertical, rotatable screwinclosed by a housing having an opening towards the adjacent side wallof the vat, the latter provided with a recessed plate having a lockange, a clamp nut threaded on said screw and provided with a locking lipprojecting thru said opening for engaging with said lock iiange.

6. The combination described by claim 5 with the base of said housingadapted to bear on said lock-bar and means for holding said housingfirmly against the adjacent side wall of the vat.

'7. In combination with a vat a flat screen assembly comprising adjacentrectangular sections, each composed of sides, ends, a transverse middlebar, and screen plates, said middle bar being spaced from the bottom ofthe frame, the middle bar provided with a locking head for engagingadjacent screen plates, means for connecting the opposed sides ofadjacent frame sections so spaced as to receive a screen plate lock-barbetween them, a screen plate lock-bar adapted to be inserted betweensaid opposed frame sides, said lock-bar provided with a head adapted toengage the sides of adjacent screen plates, screw clamps for securingsaid lock-bars in place, the side walls of the vat provided with-recessed plates having a. lock-flange, and said screw clamps includinga screw operated lockinglip engaging with said lock ange, the base ofsaid housing provided with a lug adapted to be inserted between adjacentscreen plates and bearing against the end of said screen lock-bar,whereby to prevent the tilting of the screw clamp by the engagement ofits said locking lip with said lock-flange of said wall plate.

8.,In combination with a vat a flat screen assembly comprising adjacentrectangular sections, each composed of sides, ends, a transverse middlebar, and screen plates, said middle bar being spaced from the bottom ofthe frame, the middle bar provided with a locking head for engagingadjacent screen plates, means for connecting the opposed sides ofadjacent frame sections so spaced as to receive a screen plate lock-barbetween them, a screen plate lock-bar adapted to be inserted betweensaid opposed frame sides, said lock-bar provided with a head adapted toengage the sides of adjacent screen plates, screw clamps for securingsaid lock-bars in place, the side walls of the vat provided withrecessed plates having a lock-flange, and said screw clamps including ascrew operated locking lip engaging with said lock-flange, a series ofoverlying bars extending over the ends of said screen plates adjacentthe sides of the vat, each of said screw clamps being provided with ahousing interposed between and connecting the adjacent ends oi saidoverlying bars, adapted to hold down said overlying bars, and to formtherewith continuous wall surfaces constituting the inner sides of atrough over the screen plates.

9. The combination described by claim with with the base of said housingadapted to bear on said lock-bar, means for holding said housing rmlyagainst the adjacent side wall of the vat, and aseries of overlying barsextending over the ends of said screen plates adjacent the sides of thevat, the housings of said screw clamps being interposed between andconnecting the adjacent ends of said overlying bars, adapted to holddown said overlying bars, and to form therewith continuous wall surfacesconstituting the inner sides of a trough over the screen plates.

10. In combination with a vat a flat screen assembly comprising adjacentrectangular sections, each composed of sides, ends, a transverse middlebar, and screen plates, said middle bar being spaced from the bottom ofthe frame, the middle bar provided with a locking head for engagingadjacent screen plates, means for connecting the opposed sides ofadjacent frame sections so spaced as to receive a screen plate lock-barbetween them, a screen plate lock-bar adapted to be inserted betweensaid opposed frame sides, said lock-bar provided with a head adapted toengage the sides of adjacent screen plates, means for securing saidlock-bars in place, such means comprising a vertical, rotatable screwinclosed by a housing having an opening towards the adjacent side wallof the vat, the latter provided with a recessed plate having a lockange, a

clamp nut threaded on said screw and provided with a locking lipprojecting thru said opening for engaging with saidlock flange, the baseof said housing adapted to bear on said lock-bar, the base of saidhousing provided with a lug adapted to be inserted between adjacentscreen plates and bearing against the end of said screen lock-bar,whereby to prevent the tilting of the screw clamp by the engagement ofits said locking lip with said lock flange of said wall plate, a seriesof overlying bars extending over the ends of said screen plates adjacentthe sides of the vat, the housings of said screw clamps being interposedbetween and connecting the adjacent ends of said overlying bars, adaptedto hold down said overlying bars, and to form therewith continuous wallsurfaces constituting the inner sides of a trough over the screenplates.

11. The combination described by claim 10 with the sides of saidoverlying bars provided with sealing packing strips on their bottom faceand also on their face adjacent to the vat side, and withthe housing ofsaid rotatable screw adapted to enter said recessed plate in theadjacent side wall of the vat and to form therewith a complete inclosurefor said screw clamp.

12'. In a flat screen assembly a rectangular metal frame sectionconsisting of interttin'g side members, end members, and a middle bar,said middle bar provided with a screen plate holding head, and means forconnecting the opposed sides of adjacent frame sections in spacedrelation.

13. In combination with a vat, a at screen assembly comprisingrectangular metal frame sections, each consisting of intertting sidemembers, end members, an'd a middle bar, said middle bar provided with ascreen plate holding head, and means for connecting the opposed sides ofadjacent frame sections in spaced relation.

14. In a iiat screen assembly rectangular metal frame sections, eachconsisting of intertting side members, end members, and a middle bar,said middle bar provided with a screen plate holding head, and means forconnecting the opposed sides of adjacent frame sections in spacedrelation, a lock-bar adapted to be inserted in the space and to engagethe sides of adjacent screen plates, and means for securing saidlock-bar in place.

15. In combination with a vat, a flat screen' assembly, comprisingone-piece, rectangular metal frame sections, each consisting ofintertting side members, end members, and a middle bar, said middle barprovided with a screen plate holding head, and means for connecting theopposed sides of adjacent frame sections in spaced relation, a lock-baradapted to be inserted in the space and to engage the sides of adjacentscreen plates, means for securing said lock-bar in place, such meanscomprising a vertical, rotatable screw inclosed by a housing having anopening towards the adjacent side wall of the vat, the latter providedwith a recessed plate having a lock flange, a clamp nut threaded on saidscrew and provided with a locking lip projecting thru said opening forengaging with said lock flange.

16. In combination with a vat, a flat screen assembly comprisingrectangular screen frame sections adapted to support screen plates, saida rotatable screw inclosed by a housing having' an opening facing theadjacent side wall of the vat, a nut threaded on said screw, said nutprovided with a locking lip projecting thru said opening, the side wallsof the vat provided with a recessed plate having a flange adapted to beengaged by said locking lip.

17. The combination described by claim 16 with two sides of the housingof said screw clamp adapted to enter said recessed plate in the sidewall of the vat.

18. The combination described by claim 16 with the base of said housingprovided with a lug adapted to be inserted between adajacent screenplates and bearing against the end of said screen plate lock-bar,whereby to prevent the base of said housing sliding away from theadjacent side wall of the vat when said locking lip is forced againstsaid iiange.

19. A flat screen assembly comprising a vat and a diaphragm, screenframe supportingv members, and screen plates, all surfaces of the vatand supporting members which come in contact with the pulp below thescreen plates being of metal, means for fastening the screen plates onthe said frame members, means for sealing the ends of screen plates withthe sides of the vat, and screw clamps for securing said sealing meansin place and for holding down said screen plates and said framesupporting members, each of said screw clamps being inclosed in a metalhousing having an opening facing the adjacent side of the vat, saidhousing adapted to form a complete inclosure for said screw clamp withthe vat side, whereby to prevent any pulp coming in contact with saidscrew clamps.

20. A lock-bar-screW-clamp for a iiat screen assembly of the characterdescribed, the clamp comprising a screw vertically journaled in anenclosing housing having an open side adapted to be fitted against theinterior face of a side of the vat, to prevent pulp entering saidhousing thru said open side, a nut threaded and axially movable on saidscrew in said housing, said nut provided with a lip projecting thru saidopen side of the housing for engagement withv an abutment provided onthe interior face of the vat side, whereby to cause the base of saidhousing to bear rmly on the adjacent end of the lock-bar.

21. A lock-bar-screw-clamp for a flat screen assembly of the characterdescribed, the clamp comprising a screw vertically journaled in anenclosing housing having an open side adapted to be tted against theinterior face of a side of the vat, to prevent pulp entering saidhousing thru said open side, a nut threaded and axially movable on saidscrew in said housing, said nut provided with a lip projecting thru saidopen side of the housing for engagement with an abutment provided on theinterior face of the vat side, whereby to cause the base of said housingto bear firmly on the adjacent end of the lock-bar, the base of thehousing provided with a lug adapted to be inserted between adjacentscreen plates and the lock-bar end to hold the base of said housing inplace.

22. A lock-bar-screw-clamp for a at screen assembly of the characterdescribed, the clamp comprising a screw vertically journaled in anenclosing housing having an open side adapted to be tted against theinterior face of a side of the vat, to prevent pulp entering saidhousing thru said open side, a nut threaded and axially movable on saidscrew in said housing,

said nut provided with a lip projecting thru said open side of thehousing for engagement with an abutment provided on the interior face ofthe vat side, whereby to cause the base of said housing to bear rmly onthe adjacent end of the lock-bar, said housing provided at the top withlateral projections adapted to be engaged rmly with the tops of the endsof longitudinal bars lining the sides of the vat, by the engagement ofsaid lip projection with said abutment of the vat side.

23. A lock-bar-screw-clamp for a flat screen assembly of the characterdescribed, the clamp comprising a screw vertically journaled in anenclosing housing having an open side adapted to be tted .against theinterior face of a side of the vat, to prevent pulp entering saidhousing thru said open side, a nut threaded and axially movable on saidscrew in said housing, said nut provided with a lip projecting thru saidopen side of the housing for engagement with an abutment provided on theinterior face of the vat side, whereby to cause the base of said housingto bear rmly on the adjacent end of the lock-bar, the base of thehousing provided With a lug adapted to be inserted between adjacentscreen plates and the lock-bar end to hold the base of said housing inplace, said housing provided at the top with lateral projections adaptedto be engaged firmly with the tops of the ends of longitudinal barslining the sides of the vat, by the engagement of said lip projectionwith said abutment of the vat side.

JOSEPH J. MORAVEC.

